The present invention relates to a process for the preparation of polymer compositions, the polymer compositions obtained by the process of the invention, method for the manufacture of composites, prepregs and the shaped articles employing the polymer compositions obtained with the process of the invention; and the manufactured products thereof. Specifically the present invention relates to a process for the preparation of polyaromatic compositions of desired molecular weight range, the compositions obtained by the process, a method for the manufacture of composites, prepregs and shaped articles with use of the compositions, and manufactured products thereof.
The use of curable compositions such as epoxy, cyanate, phenolic and like resins, both reinforced and unreinforced has been known for a long time in a wide variety of structural commercial and military applications. Sports devices, building materials, aeronautical, land and nautical vehicles have all found light weight carbon-based touch materials give enhanced performance.
More recently, classes of polyaromatic compositions comprising polyaryl thermoplastic components containing ether- and/or thioether-linked repeating units in the form of polyether aromatics and polyetherether aromatics are known for the manufacture of engineering polymers and composites having unique properties for the above structural applications in terms of strength, fracture toughness and high temperature stability and resistance.
Processes for the preparation of polyaromatics are known in xe2x80x9cPolyaromaticsxe2x80x9d, P. T. McGrail. Polymer International 41 (1996) 103-121, polyaromatics and their synthesis are reviewed. The polymers are traditionally manufactured by nucleophilic processes for the condensation of alkali metal salts of monomers with elimination of water.
The review details the synthesis of the known Victrex PES and PEEK polymers comprising repeating polyether sulphone and ketone units which are prepared from bisphenol-S and hydroquinone with a halogenated monomer, traditionally by a process which enables the manufacture in high molecular weight. The process entails heating together alkali metal salts of monomers in diphenyl sulphone (DPS), a solvent which is solid from room temperature. Water produced as a by product of reaction is eliminated at the elevated reaction temperatures employed. Since DPS is a solid at room temperature up to about 150xc2x0 C., it is not possible to precipitate the product polymer into a non-solvent at non-extreme temperatures. The solid which is formed on cooling which comprises a mixture of the desired polymer, DPS and residual salts, must be ground to a fine powder and put through a complex production cycle to remove the residual DPS and salts by leaching out. Finally, the polymer is dried.
A very accurate control of stoichiometry and polymerisation conditions is required in order to avoid leaching out polymer composition together with residual DPS and salts. This means that the molecular weight of polymer composition must be sufficiently high to give minimum solubility in extractant. This further complicates subsequent stages of injection molding, impregnating and the like by virtue of the high relative viscosity of the high molecular weight polymer components of the polymer composition, requiring processing at elevated temperatures.
The review also details the synthesis of a class of polysulphones which are prepared from bisphenol-A and DCDPS. This process traditionally entails heating together alkali metal salts of monomers in sulphoxide or sulphone, preferably dimethylsulphoxide (DMSO) under anhydrous conditions. In order to conduct the polymerisation reaction under anhydrous conditions it is necessary to form the alkali metal salts of monomers in a first stage in presence of an azeotrope, with removal of water prior to commencing the second stage polymerisation. The process is typically carried out at a limited maximum reaction temperature and even with use of highly reactive precursors it is not possible to develop high molecular weight. Moreover the process is cumbersome and costly due to the two stage nature, requiring intermediate processing for water removal, and due to the presence of azeotrope in both stages requiring isolation and processing of product polymer with non aqueous media.
Accordingly a first object of the present invention is to provide a process for preparation of polyaromatic compositions in which polymer reaction and isolation may be conducted independently, of constraints imposed by reaction components and for the removal of by-products of reaction.
A second object of the present invention is to provide a process for the preparation of polyaromatic compositions with use of an effective fluid combination enabling effective isolation of the product composition in convenient form.
A third object of the present invention is to provide a process for the preparation of polyaromatic compositions in a calculated molecular weight range of polymer which may be achieved independently of constraints imposed by the process such as solubility constraints and the like.
A fourth object of the present invention is to provide high quality injection molded, impregnated or otherwise shaped articles obtained with improved processing advantages of polymer compositions of the invention.
We have now surprisingly found that the above objects can be met in admirable manner with use of a novel process for the preparation of polyaromatic compositions.
Accordingly in its broadest aspect there is provided according to the present invention a process for the preparation of a polymer composition comprising at least one aromatic or a mixture thereof, the process comprising:
i) obtaining a reaction mixture comprising polymer precursors in a first fluid boiling in excess of 100xc2x0 C.;
ii) subjecting the reaction mixture to a first elevated temperature in excess of 100xc2x0 C. to generate the alkali metal salts of polymer precursors and the polymer reaction products thereof; and
iii) subjecting the reaction product mixture to at least a second temperature and isolating the reaction product in the form of a polymer composition which is substantially insoluble in a second fluid, from the first fluid which is substantially soluble in the second fluid, by contacting with an amount of second fluid:
wherein the process is conducted in substantial absence of an effective amount of an azeotrope.
It is a particular advantage that the process of the present invention can be carried out as an integrated single stage process. This is partially attributable to the fact that the process is self regulating or may be regulated in terms of production of volatiles in manner which is compatible with the progress of the reaction and with the reaction components themselves.
It is a further advantage of the process of the present invention that processing and isolation are integrated in manner that neither imposes constraints on the other in terms of incompatibility of components and conditions, but rather that features of processing and isolation are adapted for mutual enhancement in terms of convenience and efficiency.
Reference herein to first and second fluid is to an substance or mixtures of substances which is liquid at the first and second reaction and isolation temperatures.
Preferably the composition is soluble to less than 20% in the second fluid, more preferable to less than 10%, for example 0 to 5%. Preferably the first fluid is soluble to more than 50% in the second fluid, more preferably more than 80%, for example 85-100%.
It has surprisingly been found that the process of the invention eliminates constraints on choice of solvents such that the polymer composition may be isolated by precipitation in convenient manner as hereinbefore defined.
The first fluid suitably comprises at least one dipolar aprotic solvent which acts to promote the polymerisation reaction. Preferable, the first fluid boiling in excess of 100xc2x0 C. is selected from one or more of sulphur oxides, such as sulphoxides and sulphones, formamides, pyrrolidones, cyclic ketones and the like, for example tetramethylenesulphone (sulpholane) of formula (CH2)4S(O)2, dimethylsulphoxide (DMSO) of formula (CH3)2SO, diphenylsulfone (DPS) of formula (C6H5)2SO, dimethylformamide (DMF), dimethylacetamide (DMAC), n-methyl pyrrolidone (NMP) of formula C4H8NCH3 and cyclopentanone. A first fluid which is in the liquid phase at first and second temperatures as hereinbefore defined may nevertheless comprise a fluid mixture, of which any one or a number of components for example DPS, is not in the liquid phase at the temperatures as defined. Preferably the solvent is selected according to the reactivity of the monomers to be employed and according to the desired reaction temperature to be employed, for example the solvent boils in the range 100-200xc2x0 C. for use with highly reactive monomers or boils in excess of 200xc2x0 C. for use with less reactive monomers.
In a further advantage of the present invention it has been found that the polymers of the invention are more favourably soluble in the hereinbefore defined first fluids, whereby the process may be conducted in high concentration and/or with optimum time-temperature profiling. This results in significant processing cost savings.
Moreover, the process of the present invention is highly reproducible in terms of chemical and physical polymer properties including molecular weight range and distribution. This renders the polymer compositions particularly useful for applications imposing critical performance requirements on the polymers employed.
Preferably the second fluid is any fluid displaying the required solvent properties, for example is selected from alcohols and demineralised water or demineralised aqueous solvents and mixtures thereof. More preferably a second fluid as hereinbefore defined boils in the range 50-150xc2x0 C., most preferably 50-110xc2x0 C., and comprises water, an aqueous solvent or C1-3 alcohol, most preferably is water or methanol. It is a particular advantage that the first and second fluid boiling range are adapted for recovery of first and/or second fluids in high purity for reuse or disposal.
Prior to isolation of product, it may be desired to filter or otherwise purify, the reaction solution for the removal of any solid contaminants such as alkali metal reaction products. Preferably the purified reaction solution contains less than 1000 ppm of KCl, more preferably less than 500 ppm, most preferably less than 200 ppm, for example in the range 10-150 ppm. It is a particular advantage of the present invention that solution isolation enables purification by this means, rendering the product polymers suitable for applications which are not compatible with presence of alkali metal ions. Moreover purification enables rapid and cost effective recovers of polymers.
In a preferred embodiment of the present invention isolation is carried out by reducing the reaction mixture to a temperature in the range 90-125xc2x0 C. and contacting with a second fluid as hereinbefore defined which boils in the range 50-110xc2x0 C. Contacting with second fluid may be conducted in manner that the aggregate temperature after contacting of the second fluid is sufficiently, low as to prevent substantial loss of second fluid by evaporation, and sufficiently high as to prevent non-simultaneous phase transition.
The process of the present invention may be employed for the synthesis and isolation of amorphous or semi-crystalline polymers or mixtures thereof.
Preferably the at least one polyaromatic comprises repeating units of the formula 
wherein A is a direct link, oxygen, sulphur, xe2x80x94COxe2x80x94 or a divalent hydrocarbon radical;
R is any one or more substituents of the aromatic rings, each independently selected from hydrogen, C1-8 branched or straight chain aliphatic saturated or unsaturated aliphatic groups or moieties optionally comprising one or more heteroatoms selected from O, S, N, or halo for example Cl or F; and groups providing active hydrogen especially OH, NH2, NHRxe2x80x94 or xe2x80x94SH, where Rxe2x80x94 is a hydrocarbon group containing up to eight carbon atoms, or providing other cross-linking activity especially epoxy, (meth)acrylate, cyanate, isocyanate, acetylene or ethylene, as in vinyl, allyl or maleimide, anhydride, oxazoline and monomers containing saturation; and
wherein said at least one polyaromatic comprises reactive pendant and/or end groups.
More preferably the at least one polyaromatic comprises at least one polyaryl sulphone comprising ether-linked repeating units, optionally additionally comprising thioether-linked repeating units, the units being selected from the group consisting of
xe2x80x94(PhSO2Ph)nxe2x80x94
and optionally additionally
xe2x80x94(Ph)2xe2x80x94
wherein Ph is phenylene, n=1 to 2 and can be fractional, a=1 to 3 and can be fractional and when a exceeds 1, said phenylenes are linked linearly through a single chemical bond or a divalent group other than xe2x80x94SO2xe2x80x94 or are fused together, provided that the repeating unit xe2x80x94(PhSO2Ph)nxe2x80x94 is always present in said at least one polyarylsulphone in such a proportion that on average at least two of said units xe2x80x94(PhSO2Ph)nxe2x80x94 are in sequence in each polymer chain present, said at least one polyarylsulphone having reactive pendant and/or end groups.
Preferably the polyaromatic comprises polyether sulphone, more preferably a combination of polyether sulphone and of polyether ether sulphone linked repeating units, in which the phenylene group is meta- or para- and is preferably para and wherein the phenylenes are linked linearly through a single chemical bond or a divalent group other than sulphone, or are fused together. By xe2x80x9cfractionalxe2x80x9d reference is made to the average value for a given polymer chain containing units having various values of n or a.
Additionally, as also discussed, in said at least one polyarylsulphone, the relative proportions of the said repeating units is such that on average at least two units (PhSO2Ph)n are in immediate mutual succession in each polymer chain present and is preferably in the range 1:99 to 99:1, especially 10:90 to 90:10. respectively. Typically the ratio is in the range 25-50 (Ph)2, balance (PhSO2Ph)n. In preferred polyarylsulphones the units are:
1 X PhSO2PhXPhSO2Ph (xe2x80x9cPESxe2x80x9d) and
11 X(Ph)2 XPhSO2Ph (xe2x80x9cPESxe2x80x9d)
where X is O or S and may differ from unit to unit; the ratio is 1 to 11 (respectively) preferably between 10:90 and 80:20 especially between 10:90 and 55:45.
The preferred relative proportions of the repeating units of the polyarylsulphone may be expressed in terms of the weight percent SO2 content, defined as 100 times (weight of SO2)/(weight of average repeat unit). The preferred SO2 content is at least 22, preferably 23 to 25%. When a=1 this corresponds to PES:PEES ratio of at least 20:80. preferably in the range 35:65 to 65:35.
The above proportions refer only to the units mentioned. In addition to such units the polyarylsulphone may contain up to 50 especially up to 25% molar of other repeat units: the preferred SO2 content ranges (if used) then apply to the whole polymer. Such units may be for example of the formula 
as hereinbefore defined in which A is a direct link, oxygen, sulphur, xe2x80x94COxe2x80x94 or a divalent hydrocarbon radical. When the polyarylsulphone is the product of nucleophilic synthesis, its units may have been derived for example from one or more bisphenols and/or corresponding bisthiols or phenol-thiols selected from hydroquinone, 4,4xe2x80x2-dihydroxybiphenyl, resorcinol, dihydroxynaphthalene (2,6 and other isomers), 4,4xe2x80x2-dihydroxybenzophenone, 2,2xe2x80x2-di(4-hydroxyphenyl)propane and -methane.
If a bis-thiol is used, it may be formed in situ, that is, a dihalide as described for example below may be reacted with an alkali sulphide or polysulphide or thiosulphate.
Other examples of such additional units are of the formula 
in which Q and Qxe2x80x2, which may be the same or different, are CO or SO2; Ar is a dialent aromatic radical: and n is 0, 1, 2, or 3, provided that n is not zero where Q is SO2. Ar is preferably at least one divalent aromatic radical selected from phenylene, biphenylene or terphenylene. Particular units have the formula 
where m is 1, 2 or 3. When the polymer is the product of nucleophilic synthesis, such units may have been derived from one or more dihalides, for example selected from 4,4xe2x80x2-dihalobenzophenone, 4,4xe2x80x2bis(4-chlorophenylsulphonyl)biphenyl, 1,4,bis(4-halobenzoyl)bezene and 4,4xe2x80x2-bis(4-halobenzoyl)biphenyl.
They may of course have been derived partly from the corresponding bisphenols.
The polyaromatic may be the product of nucleophilic synthesis from halophenols and/or halothiophenols. In any nucleophilic synthesis the halogen if chlorine or bromine may be activated by the presence of a copper catalyst.
Such activation is often unnecessary if the halogen is activated by an electron withdrawing group. In any event fluoride is usually more active than chloride. Any nucleophilic synthesis of the polyaromatic is carried out preferably in the presence of one or more alkali metal salts, such as KOH, NaOH or K2CO3 in up to 10% molar excess over the stoichiometric.
As previously mentioned, said at least one polyaromatic contains reactive end groups and/or pendant groups. End groups may be obtained by a reaction of monomers or by subsequent conversion of product polymers prior to or subsequently to isolation. Preferably groups are of formula xe2x80x94Axe2x80x2xe2x80x94Y where Axe2x80x2 is a divalent hydrocarbon group, preferably aromatic, and is a group reactive with epoxide groups or with curing agent or with like groups on other polymer molecules. Examples of Y are groups providing active hydrogen especially OH, NH2,NHRxe2x80x2 or xe2x80x94SH, where Rxe2x80x2 is a hydrocarbon group containing up to 8 carbon atoms, or providing other cross-linking reactivity especially epoxy, (meth)acrylate, cyanate, isocyanate, acetylene or ethylene, as in vinyl, allyl or maleimide, anhydride, oxazaline and monomers containing saturation.
The number average molecular weight of the polyaromatic is suitably in the range 2000 to 60000. A useful sub-range is over 9000 especially over 10000 for example 11000 to 25000, or is under 9000, especially in the range of 3000 to 11000, for example 3000 to 9000, and structurally as well as by chemical interaction increases toughness by comparison with that of the thermoset resin alone by providing zones of the tough thermoplast between cross-linked thermoset zones.
The polyaromatic prepared according to the process of the invention may be further combined with additional polymers, for example, thermoset polymers as hereinbefore described. Thermoset polymers may be selected from the group consisting of an epoxy resin, an addition-polymerisation resin, especially a bis-maleimide resin, a formaldehyde condensate resin, especially a formaldehyde-phenol resin, a cyanate resin, an isocyanate resin, a phenolic resin and mixtures of two or more thereof, and is preferably an epoxy resin derived from the mono or poly-glycidyl derivative of one or more of the group of compounds consisting of aromatic diamines, aromatic monoprimary amines, aminophenols, polyhydric phenols, polyhydric alcohols, polycarboxylic acids and the like, or a mixture thereof, a cyanate ester resin or a phenolic resin. Examples of addition-polymerisation resins are acrylics, vinyls, bis-maleimides, and unsaturated polyesters. Examples of formaldehyde condensate resins are urea, melamine and phenols.
Preferably the thermoset polymer comprises at least one epoxy, cyanate ester or phenolic resin precursor, which is liquid at ambient temperature for example as disclosed in EP-A-0 311 349. EP-A-0 365 168, EPA 91310167.1 or in PCT/GB95/01303.
An epoxy resin may be selected from N,N,Nxe2x80x2,Nxe2x80x2-tetraglycidyl diamino diphenylmethane (eg xe2x80x9cMY 9663xe2x80x9d, xe2x80x9cMY 720xe2x80x9d or xe2x80x9cMY 721xe2x80x9d sold by Ciba-Geigy) viscosity 10-20 Pa s at 50xc2x0 C.; (MY 721 is a lower viscosity version of MY720 and is designed for higher use temperatures); N,N,Nxe2x80x2,Nxe2x80x2-tetraglycidyl-bis(4-aminophenyl)-1,4-diiso-propylbenzene (eg Epon 1071 sold by Shell Chemical Co) viscosity 18-22 Poise at 110xc2x0 C.; N,N,Nxe2x80x2,Nxe2x80x2-tetraclycidyl-bis(4-amino-3,5-dimethylphenyl)-1,4-diisopropylbenzene, (eg Epon 1072 sold by Shell Chemical Co) viscosity 30-40 Poise at 110xc2x0 C.; triglycidyl ethers of p-aminophenol (eg xe2x80x9cMY 0510xe2x80x9d sold by Ciba-Geigy), viscosity 0.55-0.85 Pa s at 25xc2x0 C.; preferably of viscosity 8-20 Pa at 25xc2x0 C.; preferably this constitutes at least 25% of the epoxy components used; diglycidyl ethers of bisphenol A based materials such as 2,2-bis(4,4xe2x80x2-dihydroxy phenyl) propane (eg xe2x80x9cDE R 661xe2x80x9d sold by Dow, or xe2x80x9cEpikote 828xe2x80x9d sold by Shell), and Novolak resins preferably of viscosity 8-20 Pa s at 25xc2x0 C.; glycidyl ethers of phenol Novolak resins (eg xe2x80x9cDEN 431xe2x80x9d or xe2x80x9cDEN 438xe2x80x9d sold by Dow), varieties in the low viscosity class of which are preferred in making compositions according to the invention; diglycidyl 1,2-phthalate, eg GLY CEL A-100; diglycidyl derivative of dihydroxy diphenyl methane (Bisphenol F) (eg xe2x80x9cPY 306xe2x80x9d sold by Ciba Geigy) which is in the low viscosity class. Other epoxy resin precursors include cycloaliphatics such as 3xe2x80x2,4xe2x80x2-epoxycyclohexyl-3,4-epoxycyclohexane carboxylate (eg xe2x80x9cCY 179xe2x80x9d sold be Ciba Geigy) and those in the xe2x80x9cBakelitexe2x80x9d range of Union Carbide Corporation.
A cyanate ester resin may be selected from one or more compounds of the central formula NCOAr(YxArm)qOCN and oligomers and/or polycyanate esters and combinations thereof wherein Ar is a single or fused aromatic or substituted aromatics and combinations thereof and therebetween nucleus linked in the ortho, meta and/or para position and x=0 up to 2 and m and q=0 to 5 independently. The Y is a linking unit selected from the group consisting of oxygen, carbonyl, sulphur, sulphur oxides, chemical bond, aromatic linked in ortho, meta and/or para positions and/or CR3R2 wherein R1 and R2 are hydrogen, halogenated alkanes, such as the fluorinated alkanes and/or substituted aromatics and/or hydrocarbon units wherein said hydrocarbon units are singularly or multiply linked and consist of up to 20 carbon atoms for each R1 and/or R2 and P(R3R4Rxe2x80x24R5) wherein R3 is alkyl, aryl, alkoxy or hydroxy, Rxe2x80x24 may be equal to R4 and a singly linked oxygen or chemical bond and R5 is doubly linked oxygen or chemical bond or Si(R3R4Rxe2x80x24R6) wherein R3 and R4, Rxe2x80x24 are defined as in P(R3R4Rxe2x80x24R5) above and R5 is defined similar to R3 above. Optionally, the thermoset can consist essentially of cyanate esters of phenol/formaldehyde derived Novolaks or dicyclopentadiene derivatives thereof, an example of which is XU71787 sold by the Dow Chemical Company.
A phenolic resin may be selected from any aldehyde condensate resins derived from aldehydes such as methanal, ethanal, benzaldehyde or furfuraldehyde and phenols such as phenol, cresols, dihydric phenols, chlorphenols and C1-9 alkyl phenols, such as phenol, 3- and 4-cresol(1-methyl, 3- and 4-hydroxy benzene), catechol(2-hydroxy phenol), resorcinol(1,3-dihydroxy benzene) and quinol(1,4-dihydroxy benzene). Preferably phenolic resins comprise cresol and novolak phenols.
The thermoset polymer is suitably the product of at least partly curing a resin precursor using a curing agent and optionally a catalyst.
The weight proportion of thermoplast component in the composition is typically in the range 5 to 100%, preferably 5 to 90%, especially 5 to 50, for example 5 to 40%.
The thermoset and polyarylaromatic are suitably reacted in the presence of a curing agent to provide a resin composition. The curing agent is suitably selected from any known curing agents, for example as disclosed in EP-A-0 311 349. EPA 91310167.1. EP-A-0 365 168 or in PCT/GB95/01303, which are incorporated herein by reference, such as an amino compound having a molecular weight up to 500 per amino group, for example an aromatic amine or a guanidine derivative. Particular examples are 3,3xe2x80x2- and 4,4xe2x80x2-diaminodiphenylsulphone, (available as xe2x80x9cDDSxe2x80x9d from commercial sources), methylenedianiline, bis(4amino-3,5-dimethylphenyl)-1,4-diisopropylbenzene (available as EPON 1062 from Shell Chemical Co); bis(4-aminophenyl)-1,4-diisopropylbenzene (available as EPON 1061 from Shell Chemical Co); 4-chlorophenyl-N,N-dimethyl-urea, eg Monuron; 3,4-dichlorophenyl-N,N-dimethyl-urea, eg Diuron and dicyanodiamide (available as xe2x80x9cAmicure CG 1200 from Pacific Anchor Chemical). Other standard epoxy curing agents such as aliphatic diamines, amides, carboxylic acid anhydrides, carboxylic acids and phenols can be used if desired. If a novolak phenolic resin is used as the main thermoset component a formaldehyde Generator such as hexamethylenetetraamine (HMT) is typically used as a curing agent.
Conventionally, and as described in EP-A-0 311 349 or in PCT/GB95/01303, a catalyst for the epoxy resin component curing agent reaction may also be used, typically a Lewis acid or a base.
The process of the invention is carried out using polymer precursors as hereinbefore defined. Specifically the precursors comprise one or more dihalides as hereinbefore defined, one or more bisphenols as hereinbefore defined as repeating units, in addition to a substituted monophenol in which the substituent is a reactive group Y as hereinbefore defined adapted to end cap the polymer chains and an alkali metal salt, as hereinbefore defined which serves to ensure formation of bisphenates by elimination of water from bisphenols. The precursors providing repeating units are suitably provided in a first fluid as hereinbefore defined and degassed. The alkali metal salt, preferably potassium carbonate is suitably added to the reaction mixture which is subjected to at least a first elevated temperature in excess of 100xc2x0 C. for extended periods as desired in order to allow the salts of monomers to form and react. Preferably the reaction mixture is subjected to at least a first elevated temperature in successive ranges, for example in a first range for a first period, a second range in excess of the first for a second period and a third range in excess of the first and second for a further period. For lower reactivity monomers for example, the first elevated temperatures is suitably of the order 150-250xc2x0 C. preferably in successive ranges of 150-200xc2x0 C., 180-220xc2x0 C., and 200-250xc2x0 C. respectively, each being maintained for a period of up to 5 hours, for example of 10-60 minutes, preferably 20-50 minutes for the first and second periods and in excess of 3 hours for the third period.
It should be appreciated that any time-temperature profile may be employed which provides for reaction of the precursors as hereinbefore defined. It is a particular advantage that a profile as hereinbefore defined may be employed to provide excellent process control and end group control leading to desired molecular weight distribution.
The relative amounts of precursors may be selected according to the desired polymer composition. A composition comprising polyethersulphones to polyetherethersulphones in a desired ratio may therefore be obtained by employing respective proportions of bisphenol and dihalides to monophenol in the same molar amounts. Preferably the proportion of bisphenol and dihalide to monophenol is in the range of 10:90-100:0, preferably 30:70-70:30, providing the polyarylsulphone having PES:PEES of the same proportions. The reaction of precursors is allowed to proceed for a further period at elevated temperature to a desired range of polymer molecular weight. Reaction may be deemed complete after sufficient time to allow all polymer precursors to react, including a proportion of end-capping component which is introduced at the outset or during the course of the reaction or prior to isolation.
Preferably end-capping component is introduced at the outset with the polymer precursors. This has the advantage of avoiding the need to open up the reactor at a later quenching stage, which risks disturbing the reaction and introducing gaseous contaminants such as oxygen and the like. Moreover without being limited to this theory it is thought that the presence of end capping component throughout the process may lead to controlled and stable polymer chain growth which is as a result of self regulation of chain length. Such self regulation may take the form of continuous growth of chains with simultaneous chain scission by end capping components.
Alternatively end capping component may be added in a further amount of first fluid to the reacted polymer components at a further elevated temperature for a further period. This has the advantage of quenching the reaction mixture to halt the further development of molecular weight. Preferably the further elevated end-capping, or quench temperature is in the range of 200-250xc2x0 C. for a period of 30-90 minutes.
End-capping component may be the same as or different to a polymer precursor as hereinbefore defined. End caps comprising halo or hydroxy reactive groups may be obtained by addition of an excess of a component as hereinbefore defined providing the repeating units of the polyarylsulphone, for example employing a slight molar excess of the dihalide or the bisphenol and monophenol. This has the advantage of convenience and accuracy of handling the minimum number of components. Alternatively end-caps comprising amino reactive groups may be obtained by addition of a pre-determined amount of a monomer, which does not provide repeating units of the polyarylsulphone, for example of aminophenol. This has the advantage of dedicated control of end-capping stoichiometry and molecular weight development. The composition is isolated in the form of a solid phase precipitate which may be purified and dried as hereinbefore defined and according to known techniques.
The composition obtained by the process of the invention may be further converted to derivatives or analogues of the polyaromatic by reaction with a suitable functionalising or derivatising agent. For example the end caps may be modified by providing the composition in the reaction solution, or post-isolation, in a solution of a suitable solvent together with any functionalising or derivatising agent according to known techniques. Alternatively the composition may be provided in solution of a suitable solvent together with further polymers to provide curable composites according to known techniques.
In a further aspect of the invention there is provided a polymer composition obtained with the process of the present invention as hereinbefore defined.
In a further aspect of the invention there is provided the use of a first or second fluid as hereinbefore defined, in the preparation of a polymer composition as hereinbefore defined.
In a further aspect there is provided according to the invention novel intermediates of the process for the preparation of a polymer composition as hereinbefore defined.
In a further aspect there is provided according to the invention a resin formulation comprising a polyaromatic component and an additional polymer as hereinbefore defined.
In a further aspect of the invention there is provided a method for the manufacture of composites employing the compositions obtained with the process of the invention.
A resin composition is particularly suitable for fabrication of structures. including load-bearing or impact resisting structures. For this purpose it may contain a reinforcing agent such as fibres. Fibres can be added short or chopped typically of mean fibre length not more than 2 cm, for example about 6 mm. Alternatively, and preferably, the fibres are continuous and may, for example, be unidirectionally-disposed fibres or a woven fabric, ie the composite material comprises a prepreg. Combinations of both short and/or chopped fibres and continuous fibres may be utilised. The fibres may be sized or unsized. Fibres can be added typically at a concentration of 5 to 35, preferably at least 20%, by weight. For structural applications, it is preferred to use continuous fibre for example glass or carbon, especially at 30 to 70, more especially 50 to 70% by volume.
The fibre can be organic, especially of stiff polymers such as poly paraphenylene terephthalamide, or inorganic. Among inorganic fibres glass fibres such as xe2x80x9cExe2x80x9d or xe2x80x9cSxe2x80x9d can be used, or alumina, zirconia, silicon carbide, other compound ceramics or metals. A very suitable reinforcing fibre is carbon, especially as graphite. Graphite fibres which have been found to be especially useful in the invention are those supplied by Amoco under the trade designations T650-35, T650-42 and T300; those supplied by Toray under the trade designation T800-HB; and those supplied by Hercules under the trade designations AS4, AU4, IM 8 and IM 7.
Organic or carbon fibre is preferably unsized or is sized with a material that is compatible with the composition according to the invention, in the sense of being soluble in the liquid precursor composition without adverse reaction or of bonding both to the fibre and to the thermoset thermoplastic composition according to the invention. In particular carbon or graphite fibres that are unsized or are sized with epoxy resin precursor or thermoplast such as polyarylsulphone are preferred. Inorganic fibre preferably is sized with a material that bonds both to the fibre and to the polymer composition; examples are the organo-silane coupling agents applied to glass fibre.
The composition may contain for example conventional toughening agents such as liquid rubbers having reactive groups, aggregates such as glass beads, rubber particles and rubber-coated glass beads, filler such as polytetrafluoroethylene, silica, graphite, boron nitride, mica, talc and vermiculite, pigments, nucleating agents, and stabilisers such as phosphates. The total of such materials and any fibrous reinforcing agent in the composition should be at least 20% by volume, as a percentage of the total volume of the polysulphone/thermoset mixture. The percentages of fibres and such other materials are calculated on the total composition after curing at the hereinbelow defined temperatures.
Preferably the composition is used in the form of a curable resin composition as hereinbefore defined, made by mixing the polyaromatic, thermoset precursor and (at some stage) any fibrous reinforcing agent and other materials. A solvent may be present. The solvent and the proportion thereof are chosen so that the mixture of polymer and resin precursor form at least a stable emulsion, preferably a stable apparently single-phase solution. The ratio of solvent to polysulphone is suitably in the range 5:1 to 20:1 by weight. Preferably a mixture of solvents is used, for example of a halogenated hydrocarbon and an alcohol, in a ratio suitably in the range 99:1 to 85:15. Conveniently the solvents in such a mixture should boil at under 100xc2x0 C. at 1 atm pressure and should be mutually miscible in the proportions used. Alternatively the polyaromatic and thermoset or precursor can be brought together by hot melting and/or high shear
The mixture is stirred until sufficiently homogeneous. Thereafter any solvent is removed by evaporation to give a resin composition. Evaporation is suitably at 50-200xc2x0 C. and, at least in its final stages, can be at subatmospheric pressure, for example in the range 13.33 Pa to 1333 Pa (0.1 to 10 mm Hg). The resin composition preferably contains up to 5% w/w of volatile solvent, to assist flow when used to impregnate fibres. This residual solvent will be removed in contact with the hot rollers of the impregnating machine.
The curable resin composition of the invention may be cured in known manner.
Suitably the composition in form of a resin solution is transferred onto a suitable mould or tool for preparation of a panel, prepreg or the like, the mould or tool having been preheated to a desired degassing temperature. The stable emulsion is combined with any reinforcing, toughening, filling, nucleating materials or agents or the like, and the temperature is raised to initiate curing thereof. Suitably curing is carried out at elevated temperature up to 200xc2x0 C., preferably in the range of 160 to 200xc2x0 C., more preferably at about 170-190xc2x0 C., and with use of elevated pressure to restrain deforming effects of escaping gases, or to restrain void formation, suitably at pressure of up to 10 bar, preferably in the range of 3 to 7 bar abs. Suitably the cure temperature is attained by heating at up to 5xc2x0 C./min. for example 2xc2x0 C. to 3xc2x0 C./min and is maintained for the required period of up to 9 hours, preferably up to 6 hours, for example 3 to 4 hours. Pressure is released throughout and temperature reduced by cooling at up to 5xc2x0 C./min. for example up to 3xc2x0 C./min. Post-curing at temperatures in the range of 190xc2x0 C. to 200xc2x0 C. may be performed, at atmospheric pressure, employing suitable heating rates to improve the glass transition temperature of the product or otherwise.
The resin composition, possibly containing some volatile solvent already present or newly added, can be used for example as an adhesive or for coating surfaces or for making solid structures by casting possibly in a foamed state. Short fibre reinforcement may be incorporated with composition prior to curing thereof. Preferably a fibre-reinforced composition is made by passing essentially continuous fibre into contact with such resin composition. The resulting impregnated fibrous reinforcing agent may be used alone or together with other materials, for example a further quantity of the same or a different polymer or resin precursor or mixture, to form a shaped article. This technique is described in more detail in EP-A-56703, 102158 and 102159.
A further procedure comprises forming incompletely cured composition into film by for example compression moulding, extrusion, melt-casting or belt-casting, laminating such films to fibrous reinforcing agent in the form of for example a non-woven mat of relatively short fibres, a woven cloth or essentially continuous fibre in conditions of temperature and pressure sufficient to cause the mixture to flow and impregnate the fibres and curing the resulting laminate.
Plies of impregnated fibrous reinforcing agent, especially as made by the procedure of one or more of EP-A 56703, 102158, 102159, can be laminated together by heat and pressure, for example by autoclave, vacuum or compression moulding or by heated rollers, at a temperature above the curing temperature of the thermosetting resin or, if curing has already taken place, above the glass transition temperature of the mixture, conveniently at least 180xc2x0 C. and typically up to 200xc2x0 C., and at a pressure in particular in excess of 1 bar, preferably in the range of 1-10 bar.
The resulting multi-ply laminate may be anisotropic in which the fibres are continuous and unidirectional, orientated essentially parallel to one another, or quasi-isotropic in each ply of which the fibres are orientated at an angle, conveniently 45xc2x0 as in most quasi-isotropic laminates but possibly for example 30xc2x0 or 60xc2x0 or 90xc2x0 or intermediately, to those in the plies above and below. Orientations intermediate between anisotropic and quasi-isotropic, and combination laminates, may be used. Suitable laminates contain at least 4 preferably at least 8, plies. The number of plies is dependent on the application for the laminate, for example the strength required, and laminates containing 32 or even more, for example several hundred, plies may be desirable. There may be aggregates, as mentioned above in interlaminar regions. Woven fabrics are an example of quasi-isotropic or intermediate between anisotropic and quasi-isotropic.
A resin composition may be obtained employing a curing agent as disclosed in PCT/IB/00701, the contents of which are incorporated herein by reference, whereby the curable resin composition is adapted to be cured at a temperature of less than that at which the material constituting the mould or tool on or in which it is intended to cure the resin composition becomes heat sensitive in any way, and more preferably at a temperature of less than or equal to 200xc2x0 C. at elevated pressure, most preferably at a temperature of less than or equal to 180xc2x0 C. at a pressure in the range of 3 to 7 bar. Suitably such composition is adapted to be cured over a period of less than or equal 6 hours, preferably less than or equal to 4 hours, most preferably of the order of less than or equal to 3 hours.
In a further aspect of the invention there is provided a method for the manufacture of a thermoset resin comprising obtaining the resin composition in a suitable mould or tool, or equivalent state in which it is to be formed subjecting the composition to a desired elevated temperature at suitable pressure, for example at atmospheric pressure and maintaining the temperature for a required period. Preferably the temperature is selected as hereinbefore defined, with reference to the temperature sensitivity of a mould or the like which is being employed or otherwise, more preferably is less than or equal to 150xc2x0 C. at elevated pressure. Preferably the time is determined as hereinbefore defined.
In a further aspect of the invention there is provided the use of a composite mould or tool to contain or support a composition according to the invention as hereinbefore defined during the forming thereof. Preferably such composite tool is constructed of any suitable unsaturated polyester or thermoset resin such as epoxy or bis-maleimides having a heat resistance in excess of the forming temperature to be employed. Reinforcement is suitably provided in the form of glass fibres. Composite moulds may be prepared in conventional manner for use according to the present invention.
In a further aspect of the invention there is provided a prepreg comprising a composition as hereinbefore defined and continuous fibres, obtained by a process as hereinbefore defined.
In a further aspect of the invention there is provided a composite comprising a pre-preg as hereinbefore defined.
In a further aspect of the invention there is provided a thermoplast or a thermoplast-modified thermoset resin shaped product comprising a composition, pre-preg or composite as hereinbefore defined, which is obtained by the method as hereinbefore defined. Preferably such product is selected from components for use in aeronautical, land or nautical vehicle, building or commercial applications.
In a further aspect of the invention there is provided a polymer composition, resin composition, composite or pre-preg as hereinbefore defined for use as an aeronautical, land or nautical vehicle, building or commercial product or component thereof.
The invention is now illustrated in non limiting manner with reference to the following examples.